If you hope to pull tasty, nutritious vegetables from your freezer next winter, you need to blanch them first. Blanching stops the action of enzymes. These naturally occur in vegetables helping them grow and ripen. The enzymes continue to act after harvest and will cause color, flavor, texture, and nutrient losses. Freezing slows down the action of enyzmes, but does not stop them.
A good example of what happens when vegetables are not blanched before freezing was shared by a participant in a freezing class. She encouraged me to share her story. To use her words, she had a "freezer full" of green beans that she froze without blanching. When she went to use some she found them mushy and flavorless and not anything she wanted to eat or serve. All her time and efforts, expense of freezer bags and electricity for the freezer, and she had to throw the beans away!
Blanching also removes air and helps vegetables to shrink so they take up less freezer space. Plant and pesticide residues and microorganisms are removed from vegetable surfaces. Peels that need removing are loosened. Blanching will actually brighten the color of vegetables.
Blanching in boiling water is the best way to blanch vegetables. Steam blanching works well for broccoli, pumpkin, sweet potatoes, and winter squash. Microwave blanching is not recommended.
It is important to follow blanching directions precisely. Timing is crucial. Over blanching will cause vegetables to start cooking and quality will be lost. Underblanching has been found to stimulate enzyme activity and is worse than no blanching at all.
There is no "one time fits all" for blanching. Time will vary depending on the vegetable and its size. Blanching times and steps for water and steam blanching can be found at http://www.uga.edu/nchfp/how/freeze/blanching.html.
A few tips for success in blanching:
- Use a blancher which has a blanching basket and cover, or fit a wire basket into a large pot with a lid.
- Use one gallon water per pound of vegetables when water blanching.
- Blanch vegetables in small batches. After adding vegetables to boiling water and putting lid on pot, water should return to boil within one minute. If it doesn't you are using too much vegetable for the amount of boiling water.
- For water blanching start counting blanching time as soon as water returns to a boil. For steam blanching start counting time as soon as lid is on pot.
- Cool blanched vegetables quickly to stop cooking. Plunge basket into very cold water and change the water frequently, or use ice water. If ice is used to cool you will need about one pound ice per pound of vegetables.
- Vegetables should cool in about the same amount of time as they were blanched.
- Drain vegetables well after cooling since extra moisture can cause loss of quality when vegetables are frozen.
- Once cooled and drained, quickly move vegetables to freezer container and put into freezer.
As with many "rules" there is often an exception. It is okay to freeze onions, sweet and hot peppers, and raw tomatoes without blanching. Visit the following link at the University of Nebraska-Lincoln Extension for directions on freezing onions. This link will give links to freezing peppers and tomatoes. http://lancaster.unl.edu/food/ciq-onions.shtml.